internet.docx

Contents

Unit 1: Networking

Introduction to Networks................................................................................................................................3

Primary Network Components..........................................................................Error! Bookmark not defined.

Type of Networks:............................................................................................................................................4

Network topologies (Physical Topologies).........................................................Error! Bookmark not defined.

Network Transmission.......................................................................................Error! Bookmark not defined.

Client-Server Architecture.................................................................................Error! Bookmark not defined.

Unit 2: Internet

Concepts of Intranet, Internet & Extranet.......................................................................................................7

Uses of Internet in various fields.....................................................................................................................8

Address............................................................................................................................................................9

Services..........................................................................................................................................................12

WWW........................................................................................................................................................12

E-Mail.........................................................................................................................................................12

Chat...........................................................................................................................................................13

BBS (Bulletin Board System)......................................................................................................................14

Telnet.........................................................................................................................................................15

Search Engine............................................................................................................................................15

Meta-Search Engine...................................................................................................................................16

BLOG..........................................................................................................................................................17

PING (Packet Internet Groper)...................................................................................................................17

Unit 3: E-Commerce

E-Commerce......................................................................................................Error! Bookmark not defined.

Types of E-Commerce........................................................................................Error! Bookmark not defined.

Traditional Commerce Vs. E-Commerce............................................................Error! Bookmark not defined.

Benefits of E-Commerce....................................................................................Error! Bookmark not defined.

Limitations of E-Commerce................................................................................Error! Bookmark not defined.

Types of Electronic Payments............................................................................Error! Bookmark not defined.

EDI (Electronic Data Interchange)......................................................................Error! Bookmark not defined.

Types of Networks Networking

Unit 1: Networking

Concept Components Types of Network Network Topology Transmission Technology (Broadcasting, Point to Point) Client Server Architecture

Created By: Jenish Bhavsar (M.Sc(I.T)) 2


Introduction to Networks

Stand-alone personal computers, first introduced in the late 1970s, gave users the ability to create documents, spreadsheets, and other types of data and save them for future use. For small business user or home this was great but for larger companies, it was not enough, the larger the company, the greater the need to share information between offices, and sometimes over great distances. The stand-alone computers were not enough due to the following reasons:

Their small hard drive capacities were inefficient. To print, each computer required a printer attached locally. Sharing documents was a tedious and cumbersome task. There was no email or communication medium.

To address these problems, networks were born.

Network: A network is any collection of independent computers that communicate with one another over a

shared network medium. A computer network is a collection of two or more connected computers to communicate and share

resources. When these computers are joined in a network, people can share files and peripherals such as

modems, printers, tape backup drives, or CD-ROM drives. When networks at multiple locations are connected using services available from phone companies,

people can send e-mail, share links to the global Internet, or conduct video conferences in real time with other remote users.

Uses of Computer Networks

1. Resource Sharing: To make all programs, equipment and especially data available to anyone on the network without regard to the physical location of the resource and the user.

2. High Reliability: To provide high reliability by having alternative sources of supply. For eg: All files could be replicated on two or three machines, so if one of them is unavailable due to a hardware failure, the other copies could be used.

3. In addition, the presence of multiple CPU’s means that if one goes down, the other may be able to take over the work, although at reduced performance.

4. Saving Money: Small computer have a much better price/performance ratio than larger ones. Mainframes (room-size computers) are roughly a factor of ten times faster than Personal computers, but they cost a thousand times more. This imbalance has caused many system designers to build systems consisting of personal computers, one per user, with data kept on one or more shared file server machines. In this model, the users are called clients amd the whole arrangement is called the client-server model.

5. Scalability: The ability to increase system performance gradually as the workload grows just by adding more processors. With client-server model, new clients and new servers can be added as needed.

6. Communication medium: A computer network can provide a powerful communication among widely separated employees. Using a network, it is easy for two or more people who live far apart to write a report together.



Type of Networks:

1. LAN (Local Area Network): A network is any collection of independent computers that communicate with one another over a shared network medium. LANs are networks usually confined to a geographic area, such as a single building or a college campus. LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people.

2. WAN (Wide Area Network): WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization's LAN to the Internet. Wide area networking can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally linked using special routing protocols and filters to minimize the expense of sending data sent over vast distances

3. MAN (Metropolitan Area Network): A metropolitan area network (MAN) is a computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks (LANs) using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks (or WAN) and the Internet.


Client Server Architecture Networking


Unit 2: Internet

Concepts of Intranet, Internet and Extranet Uses of Internet in various fields Address (IP & Domain Name Address) Services

WWW Email Chat BBS Telnet Search Engine & Meta-Search Engine Blog PING

Intranet, Internet & Extranet Internet

Concepts of Intranet, Internet & Extranet

IntranetAn intranet is a set of Internet services (for example a web server) inside a local network, i.e.only

accessible from workstations of a local network, or rather a set of well-defined networks that are invisible (or inaccessible) from the outside.

ExtranetAn extranet is a private network that uses Internet technology and the public telecommunication

system to securely share part of a business's information or operations with suppliers, vendors, partners, customers, or other businesses.

An extranet can be viewed as part of a company's intranet that is extended to users outside the company.

It has also been described as a "state of mind" in which the Internet is perceived as a way to do business with other companies as well as to sell products to customers.

An extranet requires security and privacy. These can include firewall server management, the issuance and use of digital certificates or similar means of user authentication, encryption of messages, and the use of virtual private networks (VPNs) that tunnel through the public network.

InternetThe Internet (also known simply as the Net) is the world wide, publicly accessible system of

interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP).

It consists of millions of smaller business, academic, domestic, and government networks, which together carry various information and services, such as electronic mail, online chat, and the interlinked Web pages and other documents of the World Wide Web.”

ArpanetThe precursor to the Internet, ARPANET was a large wide-area network created by the United States

Defense Advanced Research Project Agency (ARPA). Established in 1969, ARPANET served as a testbed for new networking technologies, linking many

universities and research centers.Arpanet Objectives:

1. The network would continue to function even if one or many of the computers or connections in the network failed.

2. The network had to be usuable by vastly different hardware and software platforms.3. The network had to be able to automatically reroute traffic around non-functioning parts of the

network.4. The network had to be a network of networks, rahter than a network of computers.

Bandwidth In computer networking and computer science, bandwidth, network bandwidth, data bandwidth,

or digital bandwidth is a bit rate measure of available or consumed data communication resources expressed in bits/second or multiples of it (kilobits/s, megabits/s etc.).


Uses of Internet in various fields Internet

Uses of Internet in various fields

Home user: Any one can access the Internet from home through an Internet Service Provider.Educational Institution: The Internet provides teachers, researchers and students with countless

opportunities to research and exchange information. Students can get online tutorials, access e-books and libraries and can also get an online degree.

Government Organization: The Internet has made it easy for government departments and agencies to communicate with other organizations and with the citizens they serve.

Commercial Concern: A company that specializes in product marketing can use the Internet to contact suppliers and customers. Manufacturers and merchants can cover a large customer segment online and sell their products with maximum profits.

Health Organization: The Internet fosters exchanges between researchers, health professionals and patients. Patients can get online consultation from doctors and also get prescribed with relevant medicines.

Banking: Customers can access their bank accounts online, transfer funds, pay utility bills, get balance enquiry and also pay premiums for their insurance policies.

Entertainment: We can download games, songs, videos, listen online music and also socialize with friends and family using Social networking sites and chatting.

Tranportation (Railways and Airlines): Users can books their railway and flight tickets online, get train and flight schedule and pay the fare online.

Media: Media houses also have their websites to interact with their customers, get their reviews and feedbacks and also give them the latest updates continously.


Address Internet

Address

IP (Internet Protocol) The Internet Protocol (IP) is a network-layer (Layer 3) protocol that contains addressing information

and some control information that enables packets to be routed. IP has two primary responsibilities: providing connectionless, best-effort delivery of datagrams

through an internetwork; and providing fragmentation and reassembly of datagrams to support data links with different maximum-transmission unit (MTU) sizes.

IP Addressing An IP (Internet Protocol) address is a unique identifier for a node or host connection on an IP

network. An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. This is known as "dotted decimal" notation.

Format ####.####.####.#### Where ### is a decimal number between 0 and 255. Each portion separated by a decimal is referred to as an “octet.” Four octets make up an IP V4 address. In total, 32 bits make up an IP V4 address.

Each address has two basic portions: the network address and a host address. The number of bits that make up the network address and the number of bits that represent the host address is determined by the class of IP address. There are five classes of IP addresses: A, B, C, D and E. In practice, classes D and E are not used in production environments or on the Internet:

o Class A addresses begin with 0xxx, or 0 to 127 decimal. Class A is used for the large networks with many network devices. Class A is used for the large networks with many network devices.

o Class B addresses begin with 10xx, or 128 to 191 decimal. Class B addresses scheme is used for the medium sized networks. Class B addresses scheme is used for the medium sized networks.

o Class C addresses begin with 110x, or 192 to 223 decimal. Class C is used for the small networks with less than 256 devices and nodes in a network. Class C is used for the small networks with less then 256 devices and nodes in a network.

o Class D addresses begin with 1110, or 224 to 239 decimal. o Class E addresses begin with 1111, or 240 to 254 decimal.

Hosts that use the Internet must have or show a public IP address that is unique. Depending on your country, various agencies assign network addresses for public use. If an organization has host machines that do not access the Internet, then any IP address can be assigned to those machines. These are referred to as private addresses.

IP Address Subnetting IP networks can be divided into smaller networks called subnetworks (or subnets). Subnetting provides the network administrator with several benefits, including extra flexibility,

more efficient use of network addresses, and the capability to contain broadcast traffic (a broadcast will not cross a router).

Subnets are under local administration. As such, the outside world sees an organization as a single network and has no detailed knowledge of the organization’s internal structure.

A subnet mask is a 32-bit number that is applied to an IP address to identify the network and node address of a host. Bits assigned to the network address are assigned a value of 1. Bits that are part of the node address are assigned a value of 0.

A given network address can be broken up into many subnetworks. For example, 172.16.1.0, 172.16.2.0, 172.16.3.0, and 172.16.4.0 are all subnets within network 171.16.0.0. (All 0s in the host portion of an address specifies the entire network.)

ARP (Address Resolution Protocol)/ RARP (Reverse ARP) For two machines on a given network to communicate, they must know the other machine’s

physical (or MAC) addresses. By broadcasting Address Resolution Protocols (ARPs), a host can dynamically discover the

MAC-layer address corresponding to a particular IP network-layer address.


Address Internet

The term address resolution refers to the process of finding an address of a computer in a network. The address is "resolved" using a protocol in which a piece of information is sent by a client process executing on the local computer to a server process executing on a remote computer. The information received by the server allows the server to uniquely identify the network system for which the address was required and therefore to provide the required address. The address resolution procedure is completed when the client receives a response from the server containing the required address.

In addition to the Reverse Address Resolution Protocol (RARP) is used to map MAC-layer addresses to IP addresses.

RARP, which is the logical inverse of ARP, might be used by diskless workstations that do not know their IP addresses when they boot. RARP relies on the presence of a RARP server with table entries of MAC-layer-to-IP address mappings.

Domain Name A domain name is an identification string that defines a realm of administrative autonomy,

authority, or control in the Internet. Domain names are formed by the rules and procedures of the Domain Name System (DNS).

Domain names are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains .com, .net and .org, and the country code top-level domains (ccTLDs) such as .in, .us, .ca, .uk, etc. Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users that wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites. The registration of these domain names is usually administered by domain name registrars who sell their services to the public.

DNS (Domain Name System) DNS is essentially the telephone directory of the Internet. Just as a phone number such as 604-

525-5555 is mapped to a name like John Smith, every device that communicates over the Internet has a unique, machine-readable IP address that is mapped to a human-readable domain name such as www.incognito.com. If you need to contact that device, you can use its domain name.

DNS supports high performance, availability, and scalability through the use of data hierarchies, data replication, and caching.

The Domain Name System (DNS) is basically a large database which resides on various computers and it contains the names and IP addresses of various hosts on the internet and various domains.

The Domain Name System is used to provide information to the Domain Name Service to use when queries are made.

The service is the act of querying the database, and the system is the data structure and data itself. Branches attach to the root to create a huge set of paths.

The domain name system database is divided into sections called zones. The name servers in their respective zones are responsible for answering queries for their zones. A zone is a subtree of DNS and is administered separately. There are multiple name servers for a zone. There is usually one primary name server and one or more secondary name servers.


Address Internet

DNS names are assigned through the Internet Registries by the Internet Assigned Number Authority (IANA).

The domain name is a name assigned to an internet domain. For example, mycollege.edu represents the domain name of an educational institution. The names microsoft.com and

3Com.com represent the domain names at those commercial companies. DNS is hierarchical in structure. A domain is a subtree of the domain name space. From the

root, the assigned generic top-level domains are: o GOV - Government body. o EDU - Educational body. o INT - International organization o NET - Networks o COM - Commercial entity. o MIL - U. S. Military.o .ORG – Organizationo .biz – Business use

Country Code top-level domain: o .IN – Indiao .AU – Australiao .CA – Canada

Firewall A firewall is a device or set of devices designed to permit

or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass.

Many personal computer operating systems include software-based firewalls to protect against threats from the public Internet.

Many routers that pass data between networks contain firewall components and, conversely, many firewalls can perform basic routing functions.

Network layer firewalls, also called packet filters, operate at a relatively low level of the TCP/IP protocol stack, not allowing packets to pass through the firewall unless they match the established rule set. The firewall administrator may define the rules; or default rules may apply.

Application-layer firewalls work on the application level of the TCP/IP stack (i.e., all browser traffic, or all telnet or ftp traffic), and may intercept all packets traveling to or from an application. They block other packets (usually dropping them without acknowledgment to the sender). In principle, application firewalls can prevent all unwanted outside traffic from reaching protected machines.


Services Internet

Services

WWWThe World-Wide Web (W3) project allows access to the universe of online information using two

simple user interface operations. It operates without regard to where information is, how it is stored, or what system is used to manage

it.The W3 world view is of documents referring to each other by links. For its likeness to a spider’s

construction, this world is called the Web. This simple view is known as the hypertext paradigm. The reader sees on the screen a document with sensitive parts of text representing the links. A link is followed by mere pointing and clicking.

WWW is a system of distributed servers that handle the hypermedia documents. Hypermedia authors use HTML to create hypermedia documents. HTML is a method of presenting information in which selected words or phrases in the text are hyperlinks to other, related information. Linked information can be in the form of other documents, graphics, audio files, or video files.

Web browsers access and display HTML documents on the WWW. Almost every protocol type available on the internet is accessible on the Web.WWW provides a single interface for accessing all these protocols. This creates a convenient and

user-friendly environment. It gathers all the different protocols together into a single system. E-MailElectronic mail on the internet provides quick, cost-effective transfer of messages to other E-mail

users worldwide. This is probably one of the fastest and most convenient ways of communicating and includes all the

steps of the delivery of a message to a recipient - writing, sending, receiving and saving. A received message can be handled in a variety of ways - it can be stored in a text file, forwarded to other users or just deleted.

The benefits and wonders of email include: Convenience - If a desktop computer, laptop or mobile phone is around, you can type your

email message wherever you want, save it for later use and send it at any time without having to worry about envelopes, stamps and tariffs.

Speed - Emails typically arrive within seconds or minutes — anywhere in the world, something that can be said only about a negligible number of the letters I've sent via postal mail.

Attachments - You can attach any file on your computer to an email message easily, regardless of its type and, mostly, size. It's as easy to send a long master's thesis around the world as it is to email a spread sheet, a report, pictures, or a saved game of your favorite game.

Accessibility - Emails can be stored conveniently in your email program. Good programs make it easy to organize, archive and search your emails, so any information contained in an email is always readily accessible.

Cost - Safe for the fee you pay for accessing the internet, sending and receiving emails is typically free.

How E-Mail works?1. You send your email message from your computer to your email service provider.2. Your email service provider gets the destination address. 3. Your email service provider sends the message to your friend's email service provider. 4. Your friend gets the email from her service provider.


Like a real letter (or mail), an email goes through multiple stages to get from you to your friend. As it goes through these stages (called hops in Internet jargon), it uses several rules (known as protocols). SMTP: Simple Mail Transport Protocol - These rules handle outgoing email and get your

email from your computer to your friend's service provider. POP3: Post Office Protocol - These are the rules governing incoming email. It allows you to

keep a set of messages on a server that an E-Mail can access and download to your computer. Once the email is downloaded to your computer, it is usually deleted from the server.

IMAP: Internet Mail Access Protocol - This is a different set of rules governing incoming email. IMAP is more sophisticated than POP3. It allows you to keep messages on a server that you can access from multiple computers.

LDAP: Logical Directory Access Protocol – LDAP is a server that provides an E-mail address directory for users.

An E-Mail contains the following parts: The header, a set of lines containing information about the message's transportation, such as

the sender's address, the recipient's address, or timestamps showing when the message was sent by intermediary servers. It includes the following:

o From: The sender's email address o To: The recipient's email address o Date: The date when the email was sent o Received: Various information about the intermediary servers and the date when the

message was processed. o Reply-To: A reply address. o Subject: The message's subject o Cc or Bcc- Sending carbon copies or blind carbon copies to other recipients of the

same message blindly. Message: containing the message, separated from the header by a line break. Inbox: which stores all the messages received. Outbox: which stores all the messages sent. Spam: contains unwanted messages received from anonymous user ids. Trash: contains deleted messages like our Recycle Bin.

Features of Email: Composing messages: It is possible to compose messages in an attractive way using various

fonts. Also we can spell-check before finalizing it. Address Book: where the user can save Name, full name, Address, name of organization,

designation of person, etc. Forwarding of messages: It is possible to forward any message received from, say, Mr. A to

Mr. B without replying the message. Transfer of data files: We can send/receive data files to/ from a client using attachments. Vacation-responder: A vacation auto-responder answers emails in your absence.

Chat Chat programs allow users on the Internet to communicate with each other by typing in real time. They are sometimes included as a feature of a Web site, where users can log into “chat room” to

exchange comments and information about the topics addressed on the site. Online chat may address as well point-to-point communications as well as multicast

communications from one sender to many receivers. The process whereby users of the Internet engage in Real-time conversations using their computers

is known as Online-Chatting. Inorder to engage in online chat a Chat Client (eg: Yahoo! Messenger) must Log-In to a Chat

Channel and contact a Chat-Server. There are a large number of chat channels, ranging from those which support general conversations

to those which are devoted to a specific topic. Chats can be ongoing or scheduled for a particular time and duration. Most chats are focused on a

particular topic of interest and some involve guest experts or famous people who "talk" to anyone joining the chat.

Cryptography E-Security

IRC (Internet Relay Chat) Internet Relay Chat (IRC) is a system for chatting that involves a set of rules and conventions and

client/server software. On the Web, certain sites such as Talk City or IRC networks such as the Undernetprovide servers and help you download an IRC client to your PC.

You can start a chat group (called a channel) or join an existing one. There is a protocol for discovering existing chat groups and their members. Depending on the type of network, nicknames can be reserved (registered) or just used during the session. Some channels encourage you to register a nickname that you always use and even offer space for a personal profile, picture, and personal home page link.

The channel name begins with a # sign. The channels can be limited to a single user. o /list – to list channels.o /names – Lists all available channels.o /join #<name of channel> - to join a channel.

BBS (Bulletin Board System) A Bulletin Board System (BBS) is a computer system running software that allows users to connect

and log into the system using a terminal program. Once logged in, a user can perform functions such as uploading and downloading software and

data, reading news and bulletins, and exchanging messages with other users, either through electronic-mail or in public message boards.

Many BBSes also offer on-line games, in which users can compete with each other, and BBSes with multiple phone lines often provide chat rooms, allowing users to interact with each other.

A BBS may be accessible from a dial-up modem, Telnet or the Internet. Because it originated before the Graphical User Interface (GUI) became prevalent, the BBS interface was text-based.

Most BBSes are devoted to a particular subject, although some are more general in nature. Among special interests represented on BBSes are Dentistry, Law, Guns, Multi-player games, Druidic practices and information for the disabled.

The BBS is often free, although some charge a membership or usage fee. Many BBSes have websites, and many Internet access providers have Bulletin Board Systems from which new Internet users can download the necessary software to get connected.

Usenet Newsgroup A newsgroup is a repository usually within the Usenet system, for messages posted from many

users in different locations. Usenet News is a global electronic bulletin board system in which millions of computer users

exchange information on a vast range of topics. Usenet uses the Network News Transfer Protocol (NNTP).

The major difference between Usenet news and e-mail discussion groups is the fact that Usenet messages are stored on central computers, and users must connect to these computers to read or download the messages posted to the groups.

Usenet itself is a set of machines that exchanges messages or articles, from Usenet discussion forums, called newsgroups. Newsgroup servers are hosted by various organizations and institutions.

Every host of a news server maintains agreements with other news servers to regularly synchronize. In this way news servers form a network. When a user posts to one news server, the message is stored locally. That server then shares the message with the servers that are connected to it if both carry the newsgroup, and from those servers to servers that they are connected to, and so on. For newsgroups that are not widely carried, sometimes a carrier group is used for crossposting to aid distribution.

Newsgroups are often arranged into hiearchies, theoretically making it simpler to find related newsgroups. The major hiearchies are:

o Comp.* - Discussion of computer-related topics o News.*- Discussion of Usenet itself.o Sci.* - Discussion of scientific subjects.o Rec.* - Discussion of recreational activities (e.g. games & hobbies)o Soc.* - Socialising and discussion of social issues.o Talk.* - Discussion of contentious issues such as religion and politics.o Misc.* - Miscellaneous discussion



Telnet Telnet (Telecommunications Network) is a network protocol used on the Internet or local area

network (LAN) connectinos. It provides connectivity between dissimilar operating systems. Telnet is a program that allows you to log into computers on the internet and use online databases,

library catalogs, chat services and more. There are no graphics in Telnet sessions, just text. Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers.

Through Telnet, an administrator or another user can access someone else’s computer remotely. On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but

not to actually be logged on as a user of that computer. To Telnet to a computer, you must know its address. With Telnet, you log on as a regular user with

whatever privileges you may have been granted to the specific application and data on that computer.

A Telnet command request looks like this: telnet the.libraryat.whatis.edu. The result of this request would be an invitation to log on with a userid and prompt for a password. If accepted, you would be logged on like any user who used this computer every day.

Telnet is available on the World Wide Web. A link to a Telnet resource may look like any other link, but it will launch a Telnet session to make a connection. A Telnet program must be installed on your local computer and configured to your Web Browser in order to work.

Telnet is most likely to be used by program developers and anyone who has a need to use specific applications or data located at a particular host computer.

Search Engine A web search engine is designed to search for information on the World Wide Web and FTP

servers. The search results are generally presented in a list of results and are often called hits. The

information may consist of web pages, images, information and other types of files. Some search engines also mine data available in databases or open directories.

Unlike Web directories, which are maintained by human editors, search engines operate algorithmically or are a mixture of algorithmic and human input.

A search engine operates, in the following ordero Web crawlingo Indexingo Searching

Web search engines work by storing information about many web pages, which they retrieve from the html itself. These pages are retrieved by a Web crawler (sometimes also known as a spider) — an automated Web browser which follows every link on the site.

The contents of each page are then analyzed to determine how it should be indexed (for example, words are extracted from the titles, headings, or special fields called meta tags).

Data about web pages are stored in an index database for use in later queries. A query can be a single word. The purpose of an index is to allow information to be found as quickly as possible.

When a user enters a query into a search engine (typically by using key words), the engine examines its index and provides a listing of best-matching web pages according to its criteria, usually with a short summary containing the document's title and sometimes parts of the text.

The index is built from the information stored with the data and the method by which the information is indexed.

Most search engines support the use of the boolean operators AND, OR and NOT to further specify the search query.

The engine looks for the words or phrases exactly as entered. Some search engines provide an advanced feature called proximity search which allows users to define the distance between keywords.

There is also concept-based searching where the research involves using statistical analysis on pages containing the words or phrases you search for.

As well, natural language queries allow the user to type a question in the same form one would ask it to a human. A site like this would be ask.com.

The usefulness of a search engine depends on the relevance of the result set it gives back. While there may be millions of web pages that include a particular word or phrase, some pages may be more relevant, popular, or authoritative than others.

Most search engines employ methods to rank the results to provide the "best" results first.



How a search engine decides which pages are the best matches, and what order the results should be shown in, varies widely from one engine to another. The methods also change over time as Internet usage changes and new techniques evolve.

Most Web search engines are commercial ventures supported by advertising revenue and, as a result, some employ the practice of allowing advertisers to pay money to have their listings ranked higher in search results. Those search engines which do not accept money for their search engine results make money by running search related ads alongside the regular search engine results. The search engines make money every time someone clicks on one of these ads.

Meta-Search Engine A meta-search engine is a search tool that sends user

requests to several other search engines and/or databases and aggregates the results into a single list or displays them according to their source.

Meta-search engines enable users to enter search criteria once and access several search engines simultaneously.

They operate on the premise that the Web is too large for any one search engine to index it all and that more comprehensive search results can be obtained by combining the results from several search engines. This also may save the user from having to use multiple search engines separately.

Metasearch engines create what is known as a virtual database. They do not compile a physical database or catalogue of the web. Instead, they take a user's request, pass it to several other heterogeneous databases and then compile the results in a homogeneous manner based on a specific algorithm.



BLOG A blog (a blend of the term web log) is a personal journal published on the World Wide Web

consisting of discrete entries ("posts") typically displayed in reverse chronological order so the most recent post appears first.

Blogs are usually the work of a single individual, occasionally of a small group, and often are themed on a single subject. Blog can also be used as a verb, meaning to maintain or add content to a blog.

Most good quality blogs are interactive, allowing visitors to leave comments and even message each other via GUI widgets on the blogs and it is this interactivity that distinguishes them from other static websites. In that sense, blogging can be seen as a form of social networking. Indeed, bloggers do not only produce content to post on their blogs but also build social relations with their readers and other bloggers.

Many blogs provide commentary on a particular subject; others function as more personal online diaries; yet still others function more as online brand advertising of a particular individual or company.

A typical blog combines text, images, and links to other blogs, Web pages, and other media related to its topic. The ability of readers to leave comments in an interactive format is an important part of many blogs.

Most blogs are primarily textual, although some focus on art (art blog), photographs (photoblog), videos (video blogging or vlogging), music (MP3 blog), and audio (podcasting). Microblogging is another type of blogging, featuring very short posts.

There are many different types of blogs, differing not only in the type of content, but also in the way that content is delivered or written:

Personal blogs: The personal blog, an ongoing diary or commentary by an individual, is the traditional, most common blog. One type of personal blog, referred to as a microblog, is extremely detailed and seeks to capture a moment in time. Some sites, such as Twitter, allow bloggers to share thoughts and feelings instantaneously with friends and family, and are much faster than emailing or writing.

Corporate and organizational blogs: A blog can be private, as in most cases, or it can be for business purposes. Blogs used internally to enhance the communication and culture in a corporation or externally for marketing, branding or public relations purposes are called corporate blogs. Similar blogs for clubs and societies are called club blogs, group blogs, or by similar names; typical use is to inform members and other interested parties of club and member activities.

By genre: Some blogs focus on a particular subject, such as political blogs, travel blogs (also known as travelogs), gardening blogs, house blogs, fashion blogs, project blogs, education blogs, niche blogs, classical music blogs, quizzing blogs and legal blogs (often referred to as a blawgs) or dreamlogs. Two common types of genre blogs are art blogs and music blogs. While not a legitimate type of blog, one used for the sole purpose of spamming is known as a Splog.

By media type: A blog comprising videos is called a vlog, one comprising links is called a linklog, a site containing a portfolio of sketches is called a sketchblog or one comprising photos is called a photoblog.

Consumer-generated advertising is a relatively new and controversial development and it has created a new model of marketing communication from businesses to consumers. Among the various forms of advertising on blog, the most controversial are the sponsored posts. These are blog entries or posts and may be in the form of feedback, reviews, opinion, videos, etc. and usually contain a link back to the desired site using a keyword/s.

PING (Packet Internet Groper) Ping is a computer network administration utility used to test the reachability of a host on an Internet

Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer.

Ping operates by sending Internet Control Message Protocol (ICMP) echo request packets to the target host and waiting for an ICMP response. In the process it measures the time from transmission to reception (round-trip time) and records any packet loss. The results of the test are printed in the form of a statistical summary of the response packets received, including the minimum, maximum, and the mean round-trip times.



Ping is useful for verifying connectivity between two hosts. For eg, if you were having trouble connecting to a host on another network, PING would help you verify that a valid communication path existed.

Syntax: PING IP address Ping [-q] [-v] [-R] [-c Count] [-i Wait] [-s PacketSize] Host

Ping may be abused as a simple form of denial-of-service attack in the form of a ping flood, in which the attacker overwhelms the victim with ICMP echo request packets.

A response of "Destination net unreachable" means there was no route to the destination. You need to check the routing table on the router listed in the "Reply from" address in the "Destination net unreachable" message.

A response of "Request timed out" means that there was no response to the ping in the default time period (1 second). There can be any one of the following reasons

o A router is down. o The destination host is down. o There is no route back to your computer.



Web-browser A web browser is a software application for retrieving, presenting, and traversing information

resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI) and may be a web

page, image, video, or other piece of content. Hyperlinks present in resources enable users easily to navigate their browsers to related resources.

A web browser can also be defined as an application software or program designed to enable users to access, retrieve and view documents and other resources on the Internet.

Although browsers are primarily intended to access the World Wide Web, they can also be used to access information provided by web servers in private networks or files in file systems.

The major web browsers are Firefox, Google Chrome, Internet Explorer, Opera, and Safari.

The Internet Explorer tool bar looks like the one below. The tool bar is essential for navigation and frequently performed functions.

IE Toolbar

Back - returns you to the previous page Forward - goes forward again, after your have gone back a few pages Stop - stops loading a page you have selected (useful for files that are very large) Refresh - reloads the page you requested, ignores contents of your local cache Home - returns you to the homepage Search - links you to a search engine (more about searching later) Favourites - list sites you have been to and bookmarked because you thought you may like to

return History - records where you have been by day, week and month for fast return

The address or URL of the current page you are on appears in the "Address" Bar below the tool bar.

As you browse the web, your machine saves html files and images that you request. This process is called "caching". Internet Explorer calls cached files "Temporary Internet Files". Caching is designed to speed up your experience on the web.

Also, sometimes you will see a little padlock appear (bottom right on the status bar ). This means that the page you have requested is on a "secure server" - a server that allows sensitive information to be transferred between your computer and the server you have contacted - information like your credit card details, or details of an account login.


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